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20 Cards in this Set

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Anaerobic Respiration

During exercise if insufficient oxygen is reaching the muscles they use anaerobic respiration to obtain energy.



Anaerobic respiration is the incomplete breakdown of glucose and produces lactic acid.



As the breakdown of glucose is incomplete much less energy is released than during aerobic respiration. Anaerobic respiration results in an oxygen debt that has to be repaid in order to oxidise lactic acid to carbon dioxide and water.


Anaerobic Respiration (muscle fatigue)


If muscles are subjected to long periods of vigorous activity they become fatigued (stop contracting efficiently).



One cause of muscle fatigue is the build up of lactic acid in muscles. Blood flowing through the muscles removes the lactic acid.

Characteristics

Characteristics are passed on from one generation to the next in both plants and animals.

Mendal

Proposed the idea of separately inherited factors and why the importance of this discovery was not recognised until after his death.

Chromosomes

In body cells the chromosomes are normal found in pairs. Body cells divide by mitosis.



Contain the genetic information.



In human body cells, one of the 23 pairs of chromosomes carries the genes that determine sex.


In females the sex chromosomes are the same (XX)


In males the sex chromosomes are different (XY)

Mitosis

Copies the genetic material are made.



Then the cell divides one to form two genetically identical body cells.



Occurs during growth or to produce replacement cells.



The cells of the offspring produced by asexual reproduction are produced by mitosis from the parental cells. They contain the same alleles as the parents.

Gametes

The sex cells - they only have one set of chromosome.



Cells in the reproductive organs divide to form gametes.



This process is called miosis.



When gametes join at fertilisation, a single body cell with new pairs of chromosomes is formed. A new individual then develops by this cell repeatedly dividing by mitosis.

Miosis

When cells divide to form gametes:



Copies of the genetic information are made.



Then the cell divides twice to form four gametes, each with a single set of chromosomes.

Stem Cells

Cells from human embryos and adult bone marrow, called stem cells, can be made to differentiate into many different types of cells. For example nerve cells.



Human stem cells have the ability to develop into any kind of human cell.



Treatment with stem cells may be able to help conditions such as paralysis.

Genetic Variation

Sexual reproduction gives rise to variation because when gametes fuse, one of each pair of alleles come from each parent.

Characteristics

Some characteristics are controlled by a single gene. Each gene may have different forms called alleles.



Allele

An allele that controls the development of a characteristic when it is present on only one of the chromosomes is called the dominant allele.



An allele controls the development of characteristics only if the dominant allele is not present is a recessive allele.

DNA

Chromosomes ar made up of larger molecules of DNA ( deoxyribo nucleic acid) which has a double helix structure.



A gene is a small section of DNA.



Each gene codes for a particular combination of amino acids which make a specific protein.



Each person (apart from identical twins) has unique DNA. This can be used to identify individuals in a process known as DNA fingerprinting.

Genetic Disorders

Some disorders are inherited.


Embryos can be screened for the alleles that cause these and other genetic disorders.



Polydactyly - having extra fingers or toes - is caused by a dominant allele of a gene and can therefore be passed on by only one parent who has the disorder.



Cystic fibrosis

Cystic fibrosis - (a disorder of cell membranes) must be inherited from both parents. The parents may be carriers of the disorder without actually having the disorder themselves. It is caused by a recessive allele of a gene and can therefore be passed on by parents, neither of whom has the disorder.

Speciation

Changes in the environment of plants and animals may cause them to die out. The fossil record shows that new organisms arise, flourish, and after a time become extinct.

Old and new species

Evidence for early forms of life comes from fossils.



Fossils are the remains of organisms from many years ago, which are found in rocks. Fossils may be formed in various ways:



From the hard parts of animals that do not decay easily



From parts of organisms that have not decayed because one or more of the conditions needed for decay are absent.



When parts of the organism are replaced by other materials as they decay.



As preserved traces of organisms for example footprints burrow and rootlet traces.

Soft bodied

Many early forms of life were soft bodied, which means that they have left traces behind. What traces there were have been mainly destoryed by geological activity.



Extinction

Caused by:



Changes of the environment over geological time



New predators



New diseases



New, more successful, competitors



A single catastrophic event, eg massive volcanic eruptions or collisions with asteroids



Through the cyclical nature of speciation

New species

Arise as a result of:



Isolation - two populations of a species become separated eg geographically.



Genetic variation - each population has a wide range of alleles that control their characteristics.



Natural selection - in each population, the alleles that control the characteristics which help the organism to survive are selected.



Speciation - the populations become so different that successful interbreeding is no longer possible.